| Nomurabacteria | |
|---|---|
| Scientific classification | |
| Domain: | |
| (unranked): | |
| Phylum: | Nomurabacteria |
Nomurabacteria is a candidate phylum of bacteria belonging to the CPR group. They are ultra-small bacteria that have been found in a wide variety of environments, mainly in sediments under anaerobic conditions. [1] [2]
Bacteria of this phylum share several of their characteristics with other ultra-small bacteria, nanometric size, small genomes, reduced metabolism, and low capacity to synthesize nucleotides and aminoacids. They also lack respiratory chains and the Krebs cycle. In addition, many can be endosymbionts of larger bacteria. [3] [1] [2]
Phylogenetic analyzes have suggested that Nomurabacteria and the other ultra-small bacteria make up the most basal clade of all bacteria. The archaea of the DPANN group are ultra-small archaea that share the same characteristics with these bacteria and are the most basal group of the archaeo-eukaryotic clade, although it can also be paraphyletic of eukaryotes and the other archaea as will be seen below. [3] [2]
In some phylogenetic analyzes of the proteome, ultra-small bacteria emerge outside the traditional bacterial domain and instead emerge as a paraphyletic group of traditional Bacteria and the clade composed of archaea and eukaryotes. In these analyzes Nomurabacteria turns out to be the most basal clade of all cellular organisms. [3] [2]
Proteome analyzes have shown that Nomurabacteria can be the most basal clade of cellular organisms and that the other CPR bacteria are a paraphyletic group as can be seen in the cladogram that shows the phylogenetic relationships between multiple bacterial, archaean and eukaryotes. [2]
In biology, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla.
In biological taxonomy, a domain, also dominion, superkingdom, realm, or empire, is the highest taxonomic rank of all organisms taken together. It was introduced in the three-domain system of taxonomy devised by Carl Woese, Otto Kandler and Mark Wheelis in 1990.
The three-domain system is a taxonomic classification system that groups all cellular life into three domains, namely Archaea, Bacteria and Eukarya, introduced by Carl Woese, Otto Kandler and Mark Wheelis in 1990. The key difference from earlier classifications such as the two-empire system and the five-kingdom classification is the splitting of Archaea from Bacteria as completely different organisms. It has been challenged by the two-domain system that divides organisms into Bacteria and Archaea only, as Eukaryotes are considered a clade of Archaea.
The Thermoproteota are prokaryotes that have been classified as a phylum of the domain Archaea. Initially, the Thermoproteota were thought to be sulfur-dependent extremophiles but recent studies have identified characteristic Thermoproteota environmental rRNA indicating the organisms may be the most abundant archaea in the marine environment. Originally, they were separated from the other archaea based on rRNA sequences; other physiological features, such as lack of histones, have supported this division, although some crenarchaea were found to have histones. Until 2005 all cultured Thermoproteota had been thermophilic or hyperthermophilic organisms, some of which have the ability to grow at up to 113 °C. These organisms stain Gram negative and are morphologically diverse, having rod, cocci, filamentous and oddly-shaped cells. Recent evidence shows that some members of the Thermoproteota are methanogens.
Euryarchaeota is a kingdom of archaea. Euryarchaeota are highly diverse and include methanogens, which produce methane and are often found in intestines; halobacteria, which survive extreme concentrations of salt; and some extremely thermophilic aerobes and anaerobes, which generally live at temperatures between 41 and 122 °C. They are separated from the other archaeans based mainly on rRNA sequences and their unique DNA polymerase.
Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis, and cutis. Individuals are very small, typically only 0.2–0.3 μm in size and have a very small genome size. They vary in form, although most have sterols that make the cell membrane somewhat more rigid. Many are able to move about through gliding, but members of the genus Spiroplasma are helical and move by twisting. The best-known genus in the Mollicutes is Mycoplasma. Colonies show the typical "fried-egg" appearance.
Aquifex is a bacterial genus, belonging to phylum Aquificota. There is one species of Aquifex with a validly published name – A. pyrophilus – but "A. aeolicus" is sometimes considered as species though it has no standing as a name given it has not been validly or effectively published. Aquifex spp. are extreme thermophiles, growing best at temperature of 85 °C to 95 °C. They are members of the Bacteria as opposed to the other inhabitants of extreme environments, the Archaea.
The proto-mitochondrion is the hypothetical ancestral bacterial endosymbiont from which all mitochondria in eukaryotes are thought to descend, after an episode of symbiogenesis which created the aerobic eukaryotes.
Neomura is a proposed clade of life composed of the two domains Archaea and Eukaryota, coined by Thomas Cavalier-Smith in 2002. Its name reflects the hypothesis that both archaea and eukaryotes evolved out of the domain Bacteria, and one of the major changes was the replacement of the bacterial peptidoglycan cell walls with other glycoproteins.
Monera is historically a biological kingdom that is made up of prokaryotes. As such, it is composed of single-celled organisms that lack a nucleus.
A prokaryote is a single-cell organism whose cell lacks a nucleus and other membrane-bound organelles. The word prokaryote comes from the Ancient Greek πρό (pró), meaning 'before', and κάρυον (káruon), meaning 'nut' or 'kernel'. In the two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. However in the three-domain system, based upon molecular analysis, prokaryotes are divided into two domains: Bacteria and Archaea. Organisms with nuclei are placed in a third domain: Eukaryota.
Archaea is a domain of organisms. Traditionally, Archaea only included its prokaryotic members, but this sense has been found to be paraphyletic, as eukaryotes are now known to have evolved from archaea. Even though the domain Archaea includes eukaryotes, the term "archaea" in English still generally refers specifically to prokaryotic members of Archaea. Archaea were initially classified as bacteria, receiving the name archaebacteria, but this term has fallen out of use.
Terrabacteria is a taxon containing approximately two-thirds of prokaryote species, including those in the gram positive phyla as well as the phyla "Cyanobacteria", Chloroflexota, and Deinococcota.
Evolution of cells refers to the evolutionary origin and subsequent evolutionary development of cells. Cells first emerged at least 3.8 billion years ago approximately 750 million years after Earth was formed.
Bacterial taxonomy is subfield of taxonomy devoted to the classification of bacteria specimens into taxonomic ranks.
Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers that are generally of defined size and they are flanked on both sides by conserved regions to ensure their reliability. While indels can be arbitrary inserts or deletions, CSIs are defined as only those protein indels that are present within conserved regions of the protein.
Lokiarchaeota is a proposed phylum of the Archaea. The phylum includes all members of the group previously named Deep Sea Archaeal Group, also known as Marine Benthic Group B. Lokiarchaeota is part of the superphylum Asgard containing the phyla: Lokiarchaeota, Thorarchaeota, Odinarchaeota, Heimdallarchaeota, and Helarchaeota. A phylogenetic analysis disclosed a monophyletic grouping of the Lokiarchaeota with the eukaryotes. The analysis revealed several genes with cell membrane-related functions. The presence of such genes support the hypothesis of an archaeal host for the emergence of the eukaryotes; the eocyte-like scenarios.
TACK is a group of archaea, its name an acronym for Thaumarchaeota, Aigarchaeota, Crenarchaeota, and Korarchaeota, the first groups discovered. They are found in different environments ranging from acidophilic thermophiles to mesophiles and psychrophiles and with different types of metabolism, predominantly anaerobic and chemosynthetic. TACK is a clade that is sister to the Asgard branch that gave rise to the eukaryotes. It has been proposed that the TACK clade be classified as Crenarchaeota and that the traditional "Crenarchaeota" (Thermoproteota) be classified as a class called "Sulfolobia", along with the other phyla with class rank or order. After including the kingdom category into ICNP, the proposed name of this group is kingdom Thermoproteati.
The candidate phyla radiation is a large evolutionary radiation of bacterial lineages whose members are mostly uncultivated and only known from metagenomics and single cell sequencing. They have been described as nanobacteria or ultra-small bacteria due to their reduced size (nanometric) compared to other bacteria.
Palpitomonas is a genus of biflagellated protists within the phylum Cryptista, a clade of basal eukaryotes. This genus is especially significant for understanding the early evolution of mitochondria, flagella, and the broader cryptist lineage. Palpitomonas is a key model organism for studying the phylogenetic origins of mitochondria and eukaryotic motility structures, such as flagella. One of the most common species in the genus of Palpitomonas is Palpitomonas bilix, which has been used in genomic and phylogenetic studies due to its special mitochondrial genome structure and basal phylogenetic position.